(1) Field of Invention
The present invention relates to the field of electron spin resonance (ESR) spectrometry and, more particularly, to the use of such technology to enable quantitative analysis of free radicals in a chemical species using a redesigned radio-frequency (RF) circuit architecture which results in a larger audio signal and, therefore, a more sensitive ESR spectrum.
(2) Description of Related Art
The monitoring of fluids in machinery, such as vehicles, engines, pumps, and the like, is essential to ensuring reliable operation of the machinery. Numerous systems have been developed by auto manufacturers and others for improved fluids management. Researchers have prototyped the use of viscosity sensors, dielectric sensors, chromatic sensors, oil pH sensors, miniature Fourier transform infrared spectrometers (FTIR) and x-ray fluorescence sensors, sensors of magnetic particles as of iron-derived and transition metal particles, and combinations thereof.
In this and related applications, microwave-frequency electron spin resonance (ESR) miniaturized spectrometers are disclosed for such direct sensing of such molecular changes resulting from the lubricant breakdown during vehicle usage. ESR spectroscopy is a technique for studying chemical species that have one or more unpaired electrons, such as organic and inorganic free radicals or inorganic complexes possessing a transition metal ion.
The ESR microwave system structures of the present invention, unlike the prior art, directly measure free radicals in the fluid passed through a sensor using a re-designed reflection-type radio-frequency circuit architecture employing a technique called carrier suppression. The ESR spectrometer described herein can perform the same chemical analysis as its larger counterparts; however, its tiny form factor and low cost open it up to countless new applications.